It's not necessary to do rounding for alloca operations when the requested
alignment is equal to the stack alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopRotation.cpp b/lib/Transforms/Scalar/LoopRotation.cpp
new file mode 100644
index 0000000..d35a8ed
--- /dev/null
+++ b/lib/Transforms/Scalar/LoopRotation.cpp
@@ -0,0 +1,579 @@
+//===- LoopRotation.cpp - Loop Rotation Pass ------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by Devang Patel and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements Loop Rotation Pass.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "loop-rotate"
+
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SmallVector.h"
+
+using namespace llvm;
+
+#define MAX_HEADER_SIZE 16
+
+STATISTIC(NumRotated, "Number of loops rotated");
+namespace {
+
+ class VISIBILITY_HIDDEN RenameData {
+ public:
+ RenameData(Instruction *O, Value *P, Instruction *H)
+ : Original(O), PreHeader(P), Header(H) { }
+ public:
+ Instruction *Original; // Original instruction
+ Value *PreHeader; // Original pre-header replacement
+ Instruction *Header; // New header replacement
+ };
+
+ class VISIBILITY_HIDDEN LoopRotate : public LoopPass {
+
+ public:
+ static char ID; // Pass ID, replacement for typeid
+ LoopRotate() : LoopPass((intptr_t)&ID) {}
+
+ // Rotate Loop L as many times as possible. Return true if
+ // loop is rotated at least once.
+ bool runOnLoop(Loop *L, LPPassManager &LPM);
+
+ // LCSSA form makes instruction renaming easier.
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequiredID(LCSSAID);
+ AU.addPreservedID(LCSSAID);
+ AU.addPreserved<ScalarEvolution>();
+ AU.addPreserved<LoopInfo>();
+ AU.addRequiredID(LoopSimplifyID);
+ AU.addPreservedID(LoopSimplifyID);
+ }
+
+ // Helper functions
+
+ /// Do actual work
+ bool rotateLoop(Loop *L, LPPassManager &LPM);
+
+ /// Initialize local data
+ void initialize();
+
+ /// Make sure all Exit block PHINodes have required incoming values.
+ /// If incoming value is constant or defined outside the loop then
+ /// PHINode may not have an entry for original pre-header.
+ void updateExitBlock();
+
+ /// Return true if this instruction is used outside original header.
+ bool usedOutsideOriginalHeader(Instruction *In);
+
+ /// Find Replacement information for instruction. Return NULL if it is
+ /// not available.
+ const RenameData *findReplacementData(Instruction *I);
+
+ /// After loop rotation, loop pre-header has multiple sucessors.
+ /// Insert one forwarding basic block to ensure that loop pre-header
+ /// has only one successor.
+ void preserveCanonicalLoopForm(LPPassManager &LPM);
+
+ private:
+
+ Loop *L;
+ BasicBlock *OrigHeader;
+ BasicBlock *OrigPreHeader;
+ BasicBlock *OrigLatch;
+ BasicBlock *NewHeader;
+ BasicBlock *Exit;
+ LPPassManager *LPM_Ptr;
+ SmallVector<RenameData, MAX_HEADER_SIZE> LoopHeaderInfo;
+ };
+
+ char LoopRotate::ID = 0;
+ RegisterPass<LoopRotate> X ("loop-rotate", "Rotate Loops");
+}
+
+LoopPass *llvm::createLoopRotatePass() { return new LoopRotate(); }
+
+/// Rotate Loop L as many times as possible. Return true if
+/// loop is rotated at least once.
+bool LoopRotate::runOnLoop(Loop *Lp, LPPassManager &LPM) {
+
+ bool RotatedOneLoop = false;
+ initialize();
+ LPM_Ptr = &LPM;
+
+ // One loop can be rotated multiple times.
+ while (rotateLoop(Lp,LPM)) {
+ RotatedOneLoop = true;
+ initialize();
+ }
+
+ return RotatedOneLoop;
+}
+
+/// Rotate loop LP. Return true if the loop is rotated.
+bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
+
+ L = Lp;
+
+ OrigHeader = L->getHeader();
+ OrigPreHeader = L->getLoopPreheader();
+ OrigLatch = L->getLoopLatch();
+
+ // If loop has only one block then there is not much to rotate.
+ if (L->getBlocks().size() == 1)
+ return false;
+
+ assert (OrigHeader && OrigLatch && OrigPreHeader &&
+ "Loop is not in canonical form");
+
+ // If loop header is not one of the loop exit block then
+ // either this loop is already rotated or it is not
+ // suitable for loop rotation transformations.
+ if (!L->isLoopExit(OrigHeader))
+ return false;
+
+ BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
+ if (!BI)
+ return false;
+ assert (BI->isConditional() && "Branch Instruction is not condiitional");
+
+ // Updating PHInodes in loops with multiple exits adds complexity.
+ // Keep it simple, and restrict loop rotation to loops with one exit only.
+ // In future, lift this restriction and support for multiple exits if
+ // required.
+ std::vector<BasicBlock *> ExitBlocks;
+ L->getExitBlocks(ExitBlocks);
+ if (ExitBlocks.size() > 1)
+ return false;
+
+ // Check size of original header and reject
+ // loop if it is very big.
+ if (OrigHeader->getInstList().size() > MAX_HEADER_SIZE)
+ return false;
+
+ // Now, this loop is suitable for rotation.
+
+ // Find new Loop header. NewHeader is a Header's one and only successor
+ // that is inside loop. Header's other successor is out side the
+ // loop. Otherwise loop is not suitable for rotation.
+ Exit = BI->getSuccessor(0);
+ NewHeader = BI->getSuccessor(1);
+ if (L->contains(Exit))
+ std::swap(Exit, NewHeader);
+ assert (NewHeader && "Unable to determine new loop header");
+ assert(L->contains(NewHeader) && !L->contains(Exit) &&
+ "Unable to determine loop header and exit blocks");
+
+ // Copy PHI nodes and other instructions from original header
+ // into original pre-header. Unlike original header, original pre-header is
+ // not a member of loop.
+ //
+ // New loop header is one and only successor of original header that
+ // is inside the loop. All other original header successors are outside
+ // the loop. Copy PHI Nodes from original header into new loop header.
+ // Add second incoming value, from original loop pre-header into these phi
+ // nodes. If a value defined in original header is used outside original
+ // header then new loop header will need new phi nodes with two incoming
+ // values, one definition from original header and second definition is
+ // from original loop pre-header.
+
+ // Remove terminator from Original pre-header. Original pre-header will
+ // receive a clone of original header terminator as a new terminator.
+ OrigPreHeader->getInstList().pop_back();
+ BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
+ PHINode *PN = NULL;
+ for (; (PN = dyn_cast<PHINode>(I)); ++I) {
+ Instruction *In = I;
+
+ // PHI nodes are not copied into original pre-header. Instead their values
+ // are directly propagated.
+ Value * NPV = PN->getIncomingValueForBlock(OrigPreHeader);
+
+ // Create new PHI node with two incoming values for NewHeader.
+ // One incoming value is from OrigLatch (through OrigHeader) and
+ // second incoming value is from original pre-header.
+ PHINode *NH = new PHINode(In->getType(), In->getName());
+ NH->addIncoming(PN->getIncomingValueForBlock(OrigLatch), OrigHeader);
+ NH->addIncoming(NPV, OrigPreHeader);
+ NewHeader->getInstList().push_front(NH);
+
+ // "In" can be replaced by NH at various places.
+ LoopHeaderInfo.push_back(RenameData(In, NPV, NH));
+ }
+
+ // Now, handle non-phi instructions.
+ for (; I != E; ++I) {
+ Instruction *In = I;
+
+ assert (!isa<PHINode>(In) && "PHINode is not expected here");
+ // This is not a PHI instruction. Insert its clone into original pre-header.
+ // If this instruction is using a value from same basic block then
+ // update it to use value from cloned instruction.
+ Instruction *C = In->clone();
+ C->setName(In->getName());
+ OrigPreHeader->getInstList().push_back(C);
+
+ for (unsigned opi = 0, e = In->getNumOperands(); opi != e; ++opi) {
+ if (Instruction *OpPhi = dyn_cast<PHINode>(In->getOperand(opi))) {
+ if (const RenameData *D = findReplacementData(OpPhi)) {
+ // This is using values from original header PHI node.
+ // Here, directly used incoming value from original pre-header.
+ C->setOperand(opi, D->PreHeader);
+ }
+ }
+ else if (Instruction *OpInsn =
+ dyn_cast<Instruction>(In->getOperand(opi))) {
+ if (const RenameData *D = findReplacementData(OpInsn))
+ C->setOperand(opi, D->PreHeader);
+ }
+ }
+
+
+ // If this instruction is used outside this basic block then
+ // create new PHINode for this instruction.
+ Instruction *NewHeaderReplacement = NULL;
+ if (usedOutsideOriginalHeader(In)) {
+ PHINode *PN = new PHINode(In->getType(), In->getName());
+ PN->addIncoming(In, OrigHeader);
+ PN->addIncoming(C, OrigPreHeader);
+ NewHeader->getInstList().push_front(PN);
+ NewHeaderReplacement = PN;
+ }
+
+ // "In" can be replaced by NPH or NH at various places.
+ LoopHeaderInfo.push_back(RenameData(In, C, NewHeaderReplacement));
+ }
+
+ // Rename uses of original header instructions to reflect their new
+ // definitions (either from original pre-header node or from newly created
+ // new header PHINodes.
+ //
+ // Original header instructions are used in
+ // 1) Original header:
+ //
+ // If instruction is used in non-phi instructions then it is using
+ // defintion from original heder iteself. Do not replace this use
+ // with definition from new header or original pre-header.
+ //
+ // If instruction is used in phi node then it is an incoming
+ // value. Rename its use to reflect new definition from new-preheader
+ // or new header.
+ //
+ // 2) Inside loop but not in original header
+ //
+ // Replace this use to reflect definition from new header.
+ for(unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
+ const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
+
+ if (!ILoopHeaderInfo.Header)
+ continue;
+
+ Instruction *OldPhi = ILoopHeaderInfo.Original;
+ Instruction *NewPhi = ILoopHeaderInfo.Header;
+
+ // Before replacing uses, collect them first, so that iterator is
+ // not invalidated.
+ SmallVector<Instruction *, 16> AllUses;
+ for (Value::use_iterator UI = OldPhi->use_begin(), UE = OldPhi->use_end();
+ UI != UE; ++UI) {
+ Instruction *U = cast<Instruction>(UI);
+ AllUses.push_back(U);
+ }
+
+ for (SmallVector<Instruction *, 16>::iterator UI = AllUses.begin(),
+ UE = AllUses.end(); UI != UE; ++UI) {
+ Instruction *U = *UI;
+ BasicBlock *Parent = U->getParent();
+
+ // Used inside original header
+ if (Parent == OrigHeader) {
+ // Do not rename uses inside original header non-phi instructions.
+ PHINode *PU = dyn_cast<PHINode>(U);
+ if (!PU)
+ continue;
+
+ // Do not rename uses inside original header phi nodes, if the
+ // incoming value is for new header.
+ if (PU->getBasicBlockIndex(NewHeader) != -1
+ && PU->getIncomingValueForBlock(NewHeader) == U)
+ continue;
+
+ U->replaceUsesOfWith(OldPhi, NewPhi);
+ continue;
+ }
+
+ // Used inside loop, but not in original header.
+ if (L->contains(U->getParent())) {
+ if (U != NewPhi)
+ U->replaceUsesOfWith(OldPhi, NewPhi);
+ continue;
+ }
+
+ // Used inside Exit Block. Since we are in LCSSA form, U must be PHINode.
+ if (U->getParent() == Exit) {
+ assert (isa<PHINode>(U) && "Use in Exit Block that is not PHINode");
+
+ PHINode *UPhi = cast<PHINode>(U);
+ // UPhi already has one incoming argument from original header.
+ // Add second incoming argument from new Pre header.
+ UPhi->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
+ } else {
+ // Used outside Exit block. Create a new PHI node from exit block
+ // to receive value from ne new header ane pre header.
+ PHINode *PN = new PHINode(U->getType(), U->getName());
+ PN->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
+ PN->addIncoming(OldPhi, OrigHeader);
+ Exit->getInstList().push_front(PN);
+ U->replaceUsesOfWith(OldPhi, PN);
+ }
+ }
+ }
+
+ /// Make sure all Exit block PHINodes have required incoming values.
+ updateExitBlock();
+
+ // Update CFG
+
+ // Removing incoming branch from loop preheader to original header.
+ // Now original header is inside the loop.
+ for (BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
+ I != E; ++I) {
+ Instruction *In = I;
+ PHINode *PN = dyn_cast<PHINode>(In);
+ if (!PN)
+ break;
+
+ PN->removeIncomingValue(OrigPreHeader);
+ }
+
+ // Make NewHeader as the new header for the loop.
+ L->moveToHeader(NewHeader);
+
+ preserveCanonicalLoopForm(LPM);
+
+ NumRotated++;
+ return true;
+}
+
+/// Make sure all Exit block PHINodes have required incoming values.
+/// If incoming value is constant or defined outside the loop then
+/// PHINode may not have an entry for original pre-header.
+void LoopRotate::updateExitBlock() {
+
+ for (BasicBlock::iterator I = Exit->begin(), E = Exit->end();
+ I != E; ++I) {
+
+ PHINode *PN = dyn_cast<PHINode>(I);
+ if (!PN)
+ break;
+
+ // There is already one incoming value from original pre-header block.
+ if (PN->getBasicBlockIndex(OrigPreHeader) != -1)
+ continue;
+
+ const RenameData *ILoopHeaderInfo;
+ Value *V = PN->getIncomingValueForBlock(OrigHeader);
+ if (isa<Instruction>(V) &&
+ (ILoopHeaderInfo = findReplacementData(cast<Instruction>(V)))) {
+ assert(ILoopHeaderInfo->PreHeader && "Missing New Preheader Instruction");
+ PN->addIncoming(ILoopHeaderInfo->PreHeader, OrigPreHeader);
+ } else {
+ PN->addIncoming(V, OrigPreHeader);
+ }
+ }
+}
+
+/// Initialize local data
+void LoopRotate::initialize() {
+ L = NULL;
+ OrigHeader = NULL;
+ OrigPreHeader = NULL;
+ NewHeader = NULL;
+ Exit = NULL;
+
+ LoopHeaderInfo.clear();
+}
+
+/// Return true if this instruction is used by any instructions in the loop that
+/// aren't in original header.
+bool LoopRotate::usedOutsideOriginalHeader(Instruction *In) {
+
+ for (Value::use_iterator UI = In->use_begin(), UE = In->use_end();
+ UI != UE; ++UI) {
+ Instruction *U = cast<Instruction>(UI);
+ if (U->getParent() != OrigHeader) {
+ if (L->contains(U->getParent()))
+ return true;
+ }
+ }
+
+ return false;
+}
+
+/// Find Replacement information for instruction. Return NULL if it is
+/// not available.
+const RenameData *LoopRotate::findReplacementData(Instruction *In) {
+
+ // Since LoopHeaderInfo is small, linear walk is OK.
+ for(unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
+ const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
+ if (ILoopHeaderInfo.Original == In)
+ return &ILoopHeaderInfo;
+ }
+ return NULL;
+}
+
+/// After loop rotation, loop pre-header has multiple sucessors.
+/// Insert one forwarding basic block to ensure that loop pre-header
+/// has only one successor.
+void LoopRotate::preserveCanonicalLoopForm(LPPassManager &LPM) {
+
+ // Right now original pre-header has two successors, new header and
+ // exit block. Insert new block between original pre-header and
+ // new header such that loop's new pre-header has only one successor.
+ BasicBlock *NewPreHeader = new BasicBlock("bb.nph", OrigHeader->getParent(),
+ NewHeader);
+ LoopInfo &LI = LPM.getAnalysis<LoopInfo>();
+ if (Loop *PL = LI.getLoopFor(OrigPreHeader))
+ PL->addBasicBlockToLoop(NewPreHeader, LI);
+ new BranchInst(NewHeader, NewPreHeader);
+
+ BranchInst *OrigPH_BI = cast<BranchInst>(OrigPreHeader->getTerminator());
+ if (OrigPH_BI->getSuccessor(0) == NewHeader)
+ OrigPH_BI->setSuccessor(0, NewPreHeader);
+ else {
+ assert (OrigPH_BI->getSuccessor(1) == NewHeader &&
+ "Unexpected original pre-header terminator");
+ OrigPH_BI->setSuccessor(1, NewPreHeader);
+ }
+
+ for (BasicBlock::iterator I = NewHeader->begin(), E = NewHeader->end();
+ I != E; ++I) {
+ Instruction *In = I;
+ PHINode *PN = dyn_cast<PHINode>(In);
+ if (!PN)
+ break;
+
+ int index = PN->getBasicBlockIndex(OrigPreHeader);
+ assert (index != -1 && "Expected incoming value from Original PreHeader");
+ PN->setIncomingBlock(index, NewPreHeader);
+ assert (PN->getBasicBlockIndex(OrigPreHeader) == -1 &&
+ "Expected only one incoming value from Original PreHeader");
+ }
+
+ if (DominatorTree *DT = getAnalysisToUpdate<DominatorTree>()) {
+ DT->addNewBlock(NewPreHeader, OrigPreHeader);
+ DT->changeImmediateDominator(L->getHeader(), NewPreHeader);
+ DT->changeImmediateDominator(Exit, OrigPreHeader);
+ for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
+ BI != BE; ++BI) {
+ BasicBlock *B = *BI;
+ if (L->getHeader() != B) {
+ DomTreeNode *Node = DT->getNode(B);
+ if (Node && Node->getBlock() == OrigHeader)
+ DT->changeImmediateDominator(*BI, L->getHeader());
+ }
+ }
+ DT->changeImmediateDominator(OrigHeader, OrigLatch);
+ }
+
+ if(DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>()) {
+
+ // New Preheader's dominance frontier is Exit block.
+ DominanceFrontier::DomSetType NewPHSet;
+ NewPHSet.insert(Exit);
+ DF->addBasicBlock(NewPreHeader, NewPHSet);
+
+ // New Header's dominance frontier now includes itself and Exit block
+ DominanceFrontier::iterator HeadI = DF->find(L->getHeader());
+ if (HeadI != DF->end()) {
+ DominanceFrontier::DomSetType & HeaderSet = HeadI->second;
+ HeaderSet.clear();
+ HeaderSet.insert(L->getHeader());
+ HeaderSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType HeaderSet;
+ HeaderSet.insert(L->getHeader());
+ HeaderSet.insert(Exit);
+ DF->addBasicBlock(L->getHeader(), HeaderSet);
+ }
+
+ // Original header (new Loop Latch)'s dominance frontier is Exit.
+ DominanceFrontier::iterator LatchI = DF->find(L->getLoopLatch());
+ if (LatchI != DF->end()) {
+ DominanceFrontier::DomSetType &LatchSet = LatchI->second;
+ LatchSet = LatchI->second;
+ LatchSet.clear();
+ LatchSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType LatchSet;
+ LatchSet.insert(Exit);
+ DF->addBasicBlock(L->getHeader(), LatchSet);
+ }
+
+ // If a loop block dominates new loop latch then its frontier is
+ // new header and Exit.
+ BasicBlock *NewLatch = L->getLoopLatch();
+ DominatorTree *DT = getAnalysisToUpdate<DominatorTree>();
+ for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
+ BI != BE; ++BI) {
+ BasicBlock *B = *BI;
+ if (DT->dominates(B, NewLatch)) {
+ DominanceFrontier::iterator BDFI = DF->find(B);
+ if (BDFI != DF->end()) {
+ DominanceFrontier::DomSetType &BSet = BDFI->second;
+ BSet = BDFI->second;
+ BSet.clear();
+ BSet.insert(L->getHeader());
+ BSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType BSet;
+ BSet.insert(L->getHeader());
+ BSet.insert(Exit);
+ DF->addBasicBlock(B, BSet);
+ }
+ }
+ }
+ }
+
+ // Preserve canonical loop form, which means Exit block should
+ // have only one predecessor.
+ BasicBlock *NExit = SplitEdge(L->getLoopLatch(), Exit, this);
+
+ // Preserve LCSSA.
+ BasicBlock::iterator I = Exit->begin(), E = Exit->end();
+ PHINode *PN = NULL;
+ for (; (PN = dyn_cast<PHINode>(I)); ++I) {
+ PHINode *NewPN = new PHINode(PN->getType(), PN->getName());
+ unsigned N = PN->getNumIncomingValues();
+ for (unsigned index = 0; index < N; ++index)
+ if (PN->getIncomingBlock(index) == NExit) {
+ NewPN->addIncoming(PN->getIncomingValue(index), L->getLoopLatch());
+ PN->setIncomingValue(index, NewPN);
+ PN->setIncomingBlock(index, NExit);
+ NExit->getInstList().push_front(NewPN);
+ }
+ }
+
+ assert (NewHeader && L->getHeader() == NewHeader
+ && "Invalid loop header after loop rotation");
+ assert (NewPreHeader && L->getLoopPreheader() == NewPreHeader
+ && "Invalid loop preheader after loop rotation");
+ assert (L->getLoopLatch()
+ && "Invalid loop latch after loop rotation");
+
+}